The term "profiles" as used herein is intended to refer to any cross sectional shape of extruded member containing reinforcement strands, fabric or cores. Profiles include tubes or pipe which can be reinforced by a collection of strands forming a braid or fabric.
It is known to extrude a cross-linked or cross-linkable composition and to feed the reinforcement to the extruded composition in an extrusion apparatus, the reinforcement strands being embedded in the extrusion.
The extrusion can then be vulcanized at ambient pressure. The rubber body which results can be a belt, hose, pipe or structural element.
In a conventional apparatus, due to the fact that the material has to be without pores, gas is initially extracted from the mixed components of the profiles in a degassing vacuum extruder and is then fed to the extruding head. The reinforcement of the profiles is injected continuously, via an appropriate opening from the outside, into the extruding head.
The components injected into the extruding head are combined there and leave it in the form of a finished profile not yet completely vulcanized. The production of reinforced tubes follows a similar procedure. The reinforcement strand of the tube corresponds to the reinforcement of profiles. The reinforcement strand is combined with the extruded mixture in the extruding head and leaves it uniformly coated and impregnated.
In a conventional shear head apparatus, immediately before the reinforcement is brought together with the mixture, the reinforcement comes into contact with surrounding air. As a result, air and gases of the preheated reinforcement strand are trapped in the final product and the adhesion between reinforcement strand of the tube and the cross-linkable rubber covering is reduced. This is the result of the warming of the trapped air in the extruding head and in the vulcanization apparatus with subsequent expansion of the air. Since the vulcanization can be effected without pressure, the trapped air cannot be pressed out, and in the final product, said trapped air represents a boundary layer between the reinforcement and the surrounding material. The decreased adhesion lowers the quality of the final product and in the case of reinforced tubes, it is virtually impossible to manufacture a top quality product.